The Benefits of Fiber: For Your Heart, Weight, and Energy
Dietary Fiber: Insoluble vs. Soluble
WebMD Feature
Reviewed By Brunilda
Nazario, MD
Confused about fiber? You’re not alone.
Dietary fiber is a misunderstood nutrient. Many people know it is important,
but not much more than that. This article fills you in on the two main types of
fiber – soluble and insoluble -- where to find them, and the health benefits
they provide.
Dietary fibers are found naturally
in the plants that we eat. They are parts of plant that do not break down in
our stomachs, and instead pass through our system undigested. All dietary
fibers are either soluble or insoluble. Both types of fiber are equally
important for health, digestion, and preventing conditions such as heart
disease, diabetes, obesity, diverticulitis, and constipation.
Soluble vs. Insoluble Fiber
Soluble fiber dissolves in water.
Insoluble fiber does not. To some degree these differences determine how each
fiber functions in the body and benefits your health.
Soluble fibers attract water and form a gel, which slows down digestion. Soluble
fiber delays the emptying of your stomach and makes you feel full, which helps
control weight. Slower stomach emptying may also affect blood sugar
levels and have a beneficial effect on insulin sensitivity, which may help
control diabetes. Soluble fibers can also help lower LDL (“bad”) blood
cholesterol by interfering with the absorption of dietary cholesterol.
- Sources of soluble fiber: oatmeal, oat cereal, lentils, apples, oranges, pears, oat bran, strawberries, nuts, flaxseeds, beans, dried peas, blueberries, psyllium, cucumbers, celery, and carrots.
Insoluble fibers are considered gut-healthy fiber because they have a
laxative effect and add bulk to the diet, helping prevent constipation. These
fibers do not dissolve in water, so they pass through the gastrointestinal
tract relatively intact, and speed up the passage of food and waste through
your gut. Insoluble fibers are mainly found in whole grains and vegetables.
- Sources of insoluble fiber: whole wheat, whole grains, wheat bran, corn bran, seeds, nuts, barley, couscous, brown rice, bulgur, zucchini, celery, broccoli, cabbage, onions, tomatoes, carrots, cucumbers, green beans, dark leafy vegetables, raisins, grapes, fruit, and root vegetable skins.
How Much Dietary Fiber Do You Need?
Most Americans get only about 15
grams of fiber per day in their diet. But the 2005 Dietary Guidelines for
Americans recommends about 25 grams for women under 50 and teenage girls.
Teenage boys and men under 50 (who consume more calories than women) require
upwards of 30-38 grams of dietary fiber daily.
Don’t worry about what kind of fiber
you are taking in unless you are seeking a specific health benefit, such as
eating more soluble fiber to lower cholesterol. Instead, focus on eating a
healthy diet rich in fruits, vegetables, whole grains, legumes, nuts, and
seeds. This will provide a variety of soluble and insoluble fibers and all of
the health benefits.
As you increase the fiber in your
diet, you may experience more intestinal gas. Increasing fiber gradually will
allow your body to adapt. Because some fibers absorb water, you should also
drink more water as you increase fiber.
